Art of converting phosphorites.



UNITED STATES PATENT OFFICE.

HENRY VAIL DUNHAM, 0F BAINBRIDGE, NEW YORK, ASSIGNOR T0 INACIREMACHEMICAL COMPANY, A CORPORATION OF VERMONT.

ART OF CONVERTING PHOSPHORITES.

No Drawing.

To all whom it may concern:

Be it known that I, HENRY V. DUNHAM, a citizen of the United States,residing at Bainbridge, in the county of Chenango and State of New York,have invented or discovered certain new and useful Improvements in theArt of Converting Phosphorites, of which the following is aspecification.

This invention. relates to the treatment of phosphorites or phosphaterock to render the same suitable for agricultural purposes and has forits object so to treat the phosphate rock by an inexpensive process thatthe treated product will contain a large percentage of citrate solublephosphate which is suitable for plant life and which is known in the artas available phosphate.

It is well known that phosphate exists in natural phosphorites orphosphate rock in a form not available for plant life and that suchnatural phosphate must first be made available by some chemical processof treatment before it is suitable for agricultural purposes. Manyattempts have been made to secure a large percentage of availablephosphate, as, for instance, by adding to the finely ground rock certainsalts and then heating the mixture to varying degrees in a blast furnaceor other heating furnace. In most of these attempts to secure ahighavailable content of citrate soluble or dilute citric acid solublephosphate from the insoluble phosphorites, salts such as sodium sulfateor sodium carbonate or a mixture of these have been employed, forexample as shown in my copending application 649,326, filed concurrentlyherewith. These processes so far as is known have never come intopractical commercial use for the reason that the salts also act as aflux to a greater or less extent on the phosphorites, thus causing aconsiderable amount of fusion to take place on heating. Owing to theliability of the mixtures of phosphorites and converting salts to fuseit has been found impossible to utilize such high temperatures as wouldresult in the conversion of a large amount of the insoluble phosphateinto available phosphate. The disadvantages referred to above areavoided in accordance with the present invention by utilizing inconjunction with such salts or other suitable reagent a suitablematerial which will enable a much higher temperature to be obtainedwithout fusion Specification of Letters Patent.

Patented Oct. 21 1913.

Application filed September 14, 1911. Serial No. 649,283.

and which material I term a non-flux. Of a number of such materials withwhich I have experimented I find the most suitable to be aluminaprepared from bauxite or clay since not only does the alumina act as anon-flux but it also assists in converting the insoluble phosphoritesinto available phosphates and in fact can be used in some cases withoutthe salts or other reagent for the purpose of conversion.

The proportion of alumina will vary more or less, depending upon thecomposition of the phosphate rock employed. but I find that in somecases a. small percentage. for example 5%, is sufiicient, while in othercases as much as 15% may be necessary.

In carrying this invention into effect the phosphate rock is firstground to about 80 or 100 mesh and the salts or other reagent, forexample, sodium sulfate, which may be used in the proportion of about12% to 15%, ofthe weight of the phosphate employed and the non-flux(preferably alumina, as above indicatedl is then added preferably inconjunction with a considerable amount of water. The amount of aluminapreferably employed varies considerably with the amount of sodium salts(sodium sulfate) employed, and also varies depending upon the nature ofthe phosphate rock employed, particularly the proportions and characterof the materials other than tricalcium phosphate, contained in saidrock. The mixture of rock, salts and non-flux and water is then calcinedby being subjected to a high heat depending somewhat on the grade ofrock used but preferably to a white heat; and this heating treatment iscontinued for about one hour, the length of time of the heatingtreatment depending somewhat upon the quality or grade of rock beingtreated. After the mixture has been properly calcined it is removed fromthe furnace, and when it has cooled it is ground to a fine powder offrom 80 to 100 mesh. It is then ready to be applied to the soil or mixedwith other ingredients which are generally used in the manufacture offertilizers.

By the foregoing process phosphorites may be converted into suitablecondition for use as fertilizers at very much less expense than isinvolved in the usual process of conversion, owing to thegreater amountof phosphate rendered available by the addition of the non-flux. Theproduct of this process While available, that is to say soluble inammonium citrate solution of the official strength, (1.09 specificgravity), is not soluble in water.

The term available, as used in the specification and claims, is used inthe same sense in which it is ordinarily used in the fertilizerindustry, namely, that the phosphoric acid compoundsare soluble in aneutral solution )f ammonium citrate, but are not soluble in pure water.a

I am aware that sodium chlorid has previously been used with phosphaterock to produce sodium phosphate, and I disclaim the use of sodiumchlorid in this process, for the reason that my experiments havedemonstrated that sodium chlorid is far less suitable in the productionof available phosphate from phosphate rock than is sodium sulfate, or amixture of sulfate and carbonate.

Having thus described my invention I claim and desire to secure byLetters Patent:

1. A process of converting the phosphoric acid of phosphate rock intothe available condition in a single operation, which comprises producingan intimate mixture of phosphate rock, a salt of an alkali metal capableof converting said phosphate into a form in which it is soluble inammonium citrate, but insoluble in water, and a sufficient amount ofalumina to prevent fusion of the mixture, and then heating the mixtureto substantially awhite heat until said conversion is accomplished,substantially as described.

2. A process of converting the phosphoric acid of phosphate rock intothe available condition in a single operation, which comprises producingan intimate mixture of phosphate rock, a fusible alkali metal saltcapable of converting said phosphate into citrate-soluble, but notwater-soluble condition, and a suflicient amount of a nonflux to preventfusion of the mixture, and then heating the mixture to a white heatuntil said conversion is accomplished, substantially as described.

' 3. A process of convertingthe phosphoric acid of phosphate rock intothe available condition, which com rises producing an intimate mixtureof p 05 hate rock, a sufli-' cient amount of a fusib e alkali metal saltto convert said phosphate into a form in which it is soluble in ammoniumcitrate but insoluble in water, and a sutficient amount of alumina toprevent fusion of the mixture, by mixing said materials in the presenceof sufficient .water to produce a plastic mass, and then heating themixture to a white heat until said conversion is accomplished,substantially as described.

4. A process of converting the phosphoric acid of phosphate rock intothe available condition, WhlCh comprises producing an in timate mixtureof phosphate rock, a salt of an alkali metal in amount suflicient toconvert said phosphate into a citrate-soluble, but not water-solublecondition, and a sufficient amount of alumina toprevent any substantialamount of fusion of the mixture, and then heating the mixture to a whiteheat for about an hour.

In testimony whereof I atfix my signature, in presence of two Witnesses.

I LENRY VAIL DUNHAM.

Witnesses:

A. A.DUNHAM, R. A. Wnicox;

